While vacuum-based bending actuation offers benefits such as safety and compactness in soft robotics, it is often overlooked due to its limited actuation pressure, which restricts both bending angle and force output. This study presents a crease-free, origami-inspired vacuum bending actuator that advances both state-of-the-art vacuum bending actuators and traditional origami deformation principles by introducing orderly self-folding through optimized stiffness distribution. Achieved through finite element method (FEM), this design provides several advantages: (i) Self-folding allows for high bending angles (up to 138$^{\circ }$) in a compact form. (ii) The crease-free design facilitates 3D printing from a single soft material using a consumer-level fused filament fabrication (FFF) printer, specifically thermoplastic polyurethane (TPU) with a Shore hardness of 60A, potentially higher flexibility and durability. (iii) The compact configuration enables modular design, supporting reconfiguration as demonstrated in adaptable locomotion soft robots. (iv) The large bending angles allow the actuator to wrap around objects, offering extensive contact compared to other designs. This capability, combined with its vacuum-driven mechanism, enables synergy with self-closing suction cups in an octopus-like vacuum gripper, providing large versatility and grasping force for handling a wide range of objects, from small, irregular shapes to larger, flat items.

Industrial robots are capable of moving at high speed. Each time they come into contact with their environment, e.g. to pick up an object, they decelerate to a near standstill. A solution involving a compliant pneumatic gripper and adapted trajectory plan is presented to initiate contact at a higher speed while remaining within hardware limits. By adding overload clutches in either the robot arm or gripper, tolerance to errors is provided. The key parameters such as gripper compliance and maximum allowed initial impact velocity are identified. Results show that by properly optimizing these parameters, robot picking of rigid objects can be accelerated. The complete high-speed picking solution is experimentally verified. A time reduction of 16% was obtained when making contact at 0.65 m/s.

Occupational exoskeletons are not yet frequently used at work. Previous research has indicated multiple factors (physiological, implementation-related, work-related, policy, and psycho-social) that can explain this lack of adoption. However, there is a lack of specific requirements related to these themes to improve exoskeletons and their adoption. Therefore, the goal of our research is to formulate concrete requirements for the design and implementation of exoskeletons. We used a design ethnography approach (focus groups, an interview, observations, surveys, and group interviews) with multiple stakeholders (users, designers, and potential future users). Our data suggest that potential future users of exoskeletons believe that existing exoskeletons should be improved to be adopted. Exoskeletons should be more comfortable to wear and flexible enough to support a wider range of tasks. We have formulated 49 requirements for occupational exoskeletons, and we validated and extended an existing framework. Our work encourages the improved design of future or existing exoskeletons.

Robots are more often deployed in unstructured or unpredictable environments. Particularly collisions at high speed can severely damage the drivetrains and joint bearings of robots. In order to avoid such collisions, path planners exist that adapt the robot's original trajectory online if a collision hazard is detected. These methods require additional sensors such as cameras, are computationally costly and never flawless due to occlusions. Another approach is to incorporate a cost function that promotes collision tolerance while planning the initial trajectory. The resulting impact-aware path plan minimizes the chance of robot hardware damage if a collision would occur. Two algorithms are presented to assess collision tolerance in high-speed robots, taking into account factors such as robot pose, impact direction, and maximum intermittent loading of the gearboxes and bearings. The first algorithm is more general while the second assumes the presence of joint overload clutches that decouple upon impact. These algorithms are applied to plan an impact-aware path for a custom 6-axis series clutched actuated robot that serves as use case. Both for the case with and without clutches, a generic impact-aware plan is presented as well as at least one derived, heuristic alternative. Without clutches, trajectories that are perpendicular to the end effector flange were found to be desirable, as they allow the robot to mitigate the highest collision force without overloading the gearboxes or bearings. On the other hand, with clutches, trajectories that are parallel to the end effector flange were found to be more collision tolerant. The effect of impact direction was also experimentally validated using the custom 6-axis robot. Collisions at velocities up to 1.2 m/s were mitigated through the combination of impact-aware path planning and series clutched actuation.

Robotic engineers face major challenges to solve the complex actuation needs of Human-Robot Collaboration with existing act robotic gearboxes. Available technologies comprise high-ratio Planetary Gearheads, Cycloid Drives and Harmonic Drives, inherited from conventional industrial robotics. Alternative approaches include Direct-Drive and Quasi Direct-Drive actuation strategies, which propose to cancel or substantially reduce gear ratio, in order to minimize reflected inertia and attain enough backdrivability for collaborative tasks. This paper presents the proof-of-concept validation of a novel high-ratio, Wolfrom-based, gearbox technology that follows a different approach to attain the same objective. Testing five different gearbox prototypes, we confirm the ability of the R2poweR technology to improve efficiency and backdrivability while retaining the weight and control advantages derived from the use of high reduction ratios. The result is a highly efficient, backdrivable, high-ratio gearbox with exciting Huma-Robot Collaboration potential.

Collaborative robots can help industry workers to improve their ergonomics. They can propose a safe and ergonomic posture to the workers to reduce the risk of musculoskeletal disorders. Proposing an ergonomic stance needs postural evaluation and optimization. To optimize the workers' posture, we need to run the optimization on a cost function representing the ergonomic status. The tabular ergonomic assessment methods are the most common methods used by ergonomists, but they are linear stepwise functions that are not differentiable and not suitable for optimization purposes. We propose NeuroErgo, a deep neural network model that can approximate the tabular ergonomic assessment methods more precisely than existing methods. By solving the task constraints optimization problem for any task in industry and NeuroErgo as posture cost function, a safe and ergonomic posture can be derived and recommended to the workers while accomplishing their job.

Work-related musculoskeletal disorders (MSD) are one of the major cause of injuries and absenteeism at work. These lead to important cost in the manufacturing industry. Human-robot collaboration can help decreasing this issue by appropriately distributing the tasks and decreasing the workload of the factory worker. This paper proposes a novel generic task allocation approach based on hierarchical finite-state machines for human-robot assembly tasks. The developed framework decomposes first the main task into sub-tasks modelled as state machines. Based on capabilities considerations, workload, and performance estimations, the task allocator assigns the sub-task to human or robot agent. The algorithm was validated on the assembly of a crusher unit of a smoothie machine using the collaborative Franka Emika Panda robot and showed promising results in terms of productivity thanks to task parallelization, with improvement of more than 30% of the total assembly time with respect to a collaborative scenario, where the agents perform the tasks sequentially.

Recent advances in soft robotics in academia have led to the adoption of soft grippers in industrial settings. Due to their soft bending actuators, these grippers can handle delicate objects with great care. However, due to their flexibility, the actuators are prone to out-of-plane deformations upon asymmetric loading. These undesired deformations lead to reduced grasp performance and may cause instability or failure of the grip. While the state-of-the-art contributions describe complex designs to limit those deformations, this work focuses on a complementary path investigating the material distribution. In this paper, a novel bending actuator is developed with improved out-of-plane deformation resistance by optimizing the material distribution in multi-material designs composed of two polymers with different mechanical properties. This is made possible by the strong interfacial strength of Diels-Alder chemical bonds in the used polymers, which have a self-healing capability. A Solid Isotropic Material with Penalization (SIMP) topology optimization is performed to increase the out-of-plane resistance. The actuator is simulated using FEA COMSOL in which the (hyper) elastic materials are simulated by Mooney-Rivlin models, fitted on experimental uniaxial tensile test data. This multi-material actuator and a reference single material actuator were manufactured and modeled. Via experimental characterization and validation in FEA simulations, it is shown that the actuator out-of-plane stiffness, characterized by the in-plane bending angle and out-of-plane bending angle, can be increased by an optimized multi-material composition, without changing the geometrical shape of the actuator.

Human-robot collaboration is becoming increasingly popular in the manufacturing industry, opening the door to a large range of applications by combining the complementary skills of the human worker and the robot. Collaborative robots are also a solution to decrease the operator workload and indirectly reduce the risk of occupational injuries such as musculoskeletal disorders (MSDs). The latter represents one of the major causes of absenteeism at work. Thanks to the development of human tracking devices, it is possible to monitor the operator, analyze the postures, and assess the associated MSD risk. In this paper, we present a novel ergonomics optimization framework that performs postural optimization based on the virtual element method. A feedback interface is developed whereby the user is informed about non-ergonomic postures and an improved body pose is proposed. The workpiece position controller module acts on the cobot end-effector and indirectly on the co-manipulated part in such a way that the operator’s posture is improved. The framework was validated by a user study performed on a human-robot collaboration task whereby the subject polishes a part hold by the robot. The conducted study of the user’s perception and REBA scores showed promising results.Note to Practitioners—This paper is motivated by the problem of non-ergonomic posture of workers in hybrid workcells. The proposed approach makes use of virtual elements (springs and dampers) to build a mechanical model of the human body posture and perform postural optimization. The obtained body joint angles are fed into two modules of the framework. First, a graphical interface displays the current pose of the user and proposes to him the improved posture. Second, a controller adapts the pose of the workpiece hold by the collaborative robot. This is realized by computing a displacement vector between the wrist current and optimized positions. The use of such a framework was demonstrated on a collaborative polishing task whereby the robot adjusts the position of the workpiece. After a user study test with 10 participants, joint data were collected and the REBA scores of different subtasks were measured and compared. The results from these preliminary experiments showed that the proposed approach improves the human body postures and offers a promising solution to enhance ergonomics by the robot assistance in case of robotic workcells. The conducted survey also shows an overall positive subject’s perception of the system.

New challenges arise when investigating the use of active prostheses for lower limb replacement, such as high motor power requirements, leading to increased weight and reduced autonomy. Series and parallel elasticity are often explored to reduce the necessary motor power but often the effect on the energy consumption of the prosthesis is not directly investigated, as the mechanical power properties are examined yet the motor and gearbox dynamics and efficiencies are not considered. This paper presents the investigation of a parallel elasticity compared to a series elastic actuation system used in an active ankle prosthesis. Using a matched electromechanical model of the actuator shows that the electrical efficiency can be influenced using parallel elasticity. The optimal configuration depends on the motor characteristics (dynamic behavior) and limitations, which should always be taken into account when designing optimal series and parallel springs. It has been shown that adding parallel elasticity allows to reduce the required gear ratio and thus associated friction and inertial losses. Allowing the parallel elasticity to be lockable can further influence the behavior and allow for a more versatile actuator.

Research towards (compliant) actuators, especially redundant ones like the Series Parallel Elastic Actuator (SPEA), has led to the development of drive trains, which have demonstrated to increase efficiency, torque-to-mass-ratio, power-to-mass ratio, etc. In the field of robotics such drive trains can be implemented, enabling technological improvements like safe, adaptable and energy-efficient robots. The choice of the used motor and transmission system, as well as the compliant elements composing the drive train, are highly dependent of the application and more specifically on the allowable weight and size. In order to optimally design an actuator adapted to the desired characteristics and the available space, scaling laws governing the specific actuator can simplify and enhance the reliability of the design process. Although scaling laws of electric motors and links are known, none have been investigated for a complete redundant drive train. The present study proposes to fill this gap by providing scaling laws for electric motors in combination with their transmission system. These laws are extended towards parallelization, i.e. replacing one big motor with gearbox by several smaller ones in parallel. The results of this study show that the torque/mass ratio for a motor-gearbox can not be increased by parallelization, but that it can increase the torque/volume ratio. This is however only the case if a good topology is chosen.

Successful social robot services depend on how robots can interact with users. The effective service can be obtained through smooth, engaged, and humanoid interactions in which robots react properly to a user’s affective state. This article proposes a novel Automatic Cognitive Empathy Model, ACEM, for humanoid robots to achieve longer and more engaged human-robot interactions (HRI) by considering humans’ emotions and replying to them appropriately. The proposed model continuously detects the affective states of a user based on facial expressions and generates desired, either parallel or reactive, empathic behaviors that are already adapted to the user’s personality. Users’ affective states are detected using a stacked autoencoder network that is trained and tested on the RAVDESS dataset. The overall proposed empathic model is verified throughout an experiment, where different emotions are triggered in participants and then empathic behaviors are applied based on proposed hypothesis. The results confirm the effectiveness of the proposed model in terms of related social and friendship concepts that participants perceived during interaction with the robot.

This work presents preliminary findings from a pilot study researching the complementary and similarity effect of personality of robots on children ( N=22). We aim to advance research on robot personality by using a pairwise robot comparison study, a novel method in HRI. Our findings show that the attributed gender and the voice of the robots were the main reasons given for a preference. Based on the preliminary data we hypothesize that boys have a preference for the robot with the same gender as themselves.

Robotic manipulators that are intended to interact with humans in their operating region are systems that need formal safety guarantees. Current solutions cannot handle both input and state constraints, have difficulties handling nonconvex constraints, or are computationally too expensive. To tackle these drawbacks, we analyzed a constrained control strategy, the Explicit Reference Governor (ERG), which can address both input and state constraints, and does not require any online optimization, thus making it computationally inexpensive. This paper presents the theory of the ERG for a general robotic manipulator and shows simulations for a specific 2DOF planar robotic manipulator. The proposed control scheme is able to steer the robot arm to the desired end-effector position, or an admissible approximation, in the presence of limited joint ranges, actuator saturations, and static obstacles. As a result, the ERG is a promising tool for the control of robotic manipulators subject to constraints.

Despite significant advancements in the field of wearable robots (WRs), commercial WRs still use traditional direct-drive actuation units to power their joints. On the other hand, in research prototypes compliant actuators are increasingly being used to more adequately address the issues of safety, robustness, control and overall system efficiency. The advantages of mechanical compliance are exploited in a novel modular actuator prototype designed for the knee joint. Due to its modularity, the actuator can be implemented in a knee joint of a standalone or a multi-joint lower-limbs orthosis, for use in gait rehabilitation and/or walking assistance. Differently from any other actuator used in orthotic research prototypes, it combines a Variable Stiffness Actuator (VSA) and a Parallel Elasticity Actuation (PEA) unit in a single modular system. Although independent, the units are designed to work together in order to fully mimic dynamic behavior of the human knee joint. In this paper, design aspects and functional evaluation of the new actuator are presented and a rationale for such a design in biomechanics of the human knee joint is given. The VSA subsystem is characterized in a quasi-static benchmarking environment and the results showing main performance indicators are presented.

Collaborative robots, the so-called cobots, that work together with the human, are becoming more and more popular in the industrial world. An example of an application where these robots are useful is the assembly task. In this case, the human and the robot complement each other. On one side, the human can achieve more dexterous tasks, while on the other side, the robot can assist the assembly process to lower the physical and cognitive work load, e.g. to avoid errors, and in the same way reduce absenteeism. This paper describes a novel collaborative architecture for human-robot assembly tasks. The developed architecture is composed of four modules; face recognition, gesture recognition and human-like robot behavior modules are used to enhance the human-robot interaction, while the visual inspection module is utilized for quality control during the assembly process. A collaborative task consisting of the assembly of a box whereby the robot assists the human was designed and implemented on the Baxter robot. This was used as the application use case to validate the developed collaborative architecture.

On novel actuator research in the field of cellular muscle-inspired actuators, skeletal muscles are often used as inspiration due to their modular and compact design and seemingly effortless control. Amongst others, the remaining challenges to tackle are robust designs, energy consumption minimization and control strategies. We have developed a discrete muscle-inspired actuator, in which solenoids can be overpowered and locked to recruit springs in series. This paper describes the spring and electronics design and proposes a binary actuator segmentation for increased resolution. Next, we propose and simulate a control strategy based on a lookup table, to cope with multiple discrete inputs, uni-directional force inputs and solenoid cooling time. Currently, the actuation units and springs are modular and can be tailored easily for specific applications. The resolution is maximized without under utilization of the actuator's capabilities, and our control strategy can currently control 12 motor units in real-time, which can be increased to 30. The experiments confirm the working of the control strategy.

The appearance of robots is often made arbitrary as it relies more on guidelines than on a rigorous methodology. This paper presents a novel method of using genetic algorithms (GA) to improve the appearance of social robots with human feedback. Such general methods are interesting as they do not require prior artistic experience from the designer and can integrate the end-user in the loop. As a proof of concept, we carry out a case study by applying this method to the new design of the social robot Probo. Using designer feedback, the robot is evolved from its original design over five populations composed of 15 individuals. An online survey shows that the evolved designs are significantly improved compared to the original. These results indicate the feasibility of the method employed and gives rise to the possibility of non-technical end-users influencing the design of robot morphologies adapted for specific human-robot interaction requirements.

Modern actuation schematics become increasingly ingenious by deploying springs and locking mechanisms in series and/or parallel. Many of these solutions are, however, tailored for a specific application and a general schematic that allows for drastic energy reduction remains a challenge. We have developed a series-parallel elastic actuator (SPEA) based on a symbiosis of multiple motors, springs and locking mechanisms in parallel, which we call +SPEA. This paper introduces the novel +SPEA concept. We present a first prototype, a +SPEA model and a control strategy that optimizes the energy consumption, and experiments to verify the working principle and recruitment strategy. The experiments show a good fit with the model and currently the actuator reduces the required energy in blocked output experiments by more than a factor 4.

Natural organisms have a unique property not yet available in robotics, i.e., a self-healing (SH) ability. This powerful biological healing function has inspired chemists to impart similar properties to synthetic materials to create “SH materials.” Recent developments in SH polymers led us to investigate the potential of using these materials in robotics. This paper presents an innovative approach of using SH polymers, based on the reversible Diels-Alder (DA) reaction, in a compliant actuator. Using DA polymers, a sacrificial SH mechanical fuse (SH-MF) is designed, developed, and validated by placing it in a cable-driven robotic system. The fuse is designed as weakest element and will sacrificially fail if a damaging overload occurs, protecting the compliant element and other components of the system. The experimental results showed that this SH-MF could be healed at a relatively low temperature, recovering the initial mechanical properties. This first working prototype indicates the feasibility to use SH materials in robotics. “SH robotics” will lead to more sustainable and lighter systems, and eventually to more efficient designs.

The Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator (MACCEPA) is a Variable Stiffness Actuator (VSA) where both equilibrium position and stiffness of the actuator can be controlled independently. It uses only one linear spring and has a simple design but its compactness is limited by the spring. For this reason a MACCEPA utilizing torsion spiral springs was designed, reducing the planar dimensions of the actuator. Torsion spiral springs are placed around the joint axis, allowing a more compact VSA in comparison to previous designs. To the authors' best knowledge, this is the first VSA based on torsion springs. This paper firstly presents the design of the actuator as the static equations and secondly discusses the design and production of the torsion spiral springs. The newly presented actuator is built and experiments are conducted to validate the model and feasibility of the torsion MACCEPA.

Series-Parallel Elastic Actuators (SPEA) enable variable recruitment of parallel springs and variable load cancellation. In previous work, we validated a MACCEPA-based SPEA prototype with a self-closing intermittent mechanism, to reduce motor load and improve energy efficiency. However, the mechanism only allowed for 4 parallel springs and a limited equilibrium angle range, which limits the variable load cancellation and operation range. Therefore, we developed a novel cylindrical cam mechanism for unlimited subsequent spring recruitment. This paper describes and validates the working principle of the cylindrical cam mechanism. Furthermore, the latest MACCEPA-based SPEA is presented with a maximum output torque of 40Nm and variable stiffness. Additive and traditional manufacturing techniques go hand in hand to overcome the actuator's complexity. The experiments endorse the working principle, demonstrate the variable stiffness, and prove the motor torque can be reduced to 5Nm while an output torque of 40Nm can be achieved.

Last 15 years, a wide range of self-healing (SH) materials has been developed and recently these materials are increasingly used in applications in multiple fields, like the automotive industry and aerospace. However, so far this material technology is not yet explored in robotics. The introduction of these materials in robotics will potentially reduce the over-dimensioning of current robotic systems, leading to lighter systems and eventually to more efficient designs. Compliant elements used in next generation soft robots, can be constructed from available SH-materials, making them able to autonomously heal cuts and perforations caused by sharp objects in unstructured environments. In addition, the use of SH-materials will have a beneficial impact on the life span of robotic components, reducing the required maintenance drastically. This paper presents the innovative concept of implementing a SH-mechanism in compliant actuators, using dynamic covalent polymer network systems based on the reversible Diels-Alder (DA) reaction. For two entirely different compliant actuators, a series elastic actuator (SEA) and a soft pneumatic actuator (SPA), an analysis is presented on the integration of the DA-polymers in the actuator designs. For both actuator types, a prototype was designed, developed and validated.

Two leading qualities of skeletal muscle that produce good performance in uncertain environments are damage tolerance and the ability to modulate impedance. For this reason, robotics researchers are greatly interested in discovering the key characteristics of muscles that give them these properties and replicating them in actuators for robotic devices. This paper describes a method to harness the redundancy present in muscle-like actuation systems composed of multiple motor units and shows that they have these same two qualities. By carefully choosing which motor units are recruited, the impedance viewed from the environment can be modulated while maintaining the same overall activation level. The degree to which the impedance can be controlled varies with total activation level and actuator length. Discretizing the actuation effort into multiple parts that work together, inspired by the way muscle fibers work in the human body, produces damage-tolerant behavior. This paper shows that this not only produces reasonably good resolutions without inordinate numbers of units, but gives the control system the ability to set the impedance along with the drive effort to the load.

Gestures for social robots are often preprogrammed off-line or generated by mapping motion capture data to the robot. Since these gestures are dependent on the robot's joint configuration, new joint trajectories to reach the desired postures need to be implemented when using a new robot platform with a different morphology. The method proposed here aims to minimize the workload when implementing gestures on a new robot platform and facilitate the sharing of gestures between different robots. The innovative aspect of this method is that it is constructed independently of any robot configuration, and therefore it can be used to generate gestures for different robot platforms. To calculate a posture for a certain configuration, the developed method uses a set of target gestures listed in a database and maps them to that specific configuration. The method was validated on a series of configurations, including those of existing robots.

The use of typical position controllers for robots working around humans can involve some risks when unintended physical human-robot interactions occur. In order to benefit from a proper tracking performance during normal operations, and a smooth and damped recovery from position errors due to contacts with external objects/agents, Proxy-based Sliding Mode Control was proposed. While the efficacy of this controller in fully actuated manipulators was discussed, the employment of this controller in underactuated systems has not been studied so far. This paper introduces a control scheme to implement this controller in a class of underactuated systems. Specifically, the control of flexible joint manipulators possessing passive elastic elements in series with motors is studied. The formulation of Proxy-based Sliding Mode Control is adopted according to the stability requirements of this type of dynamic systems, and a torque controller required for the regulation of the the output torque of actuation units is designed using the Feedback Linearization and the Linear Quadratic optimal control approach. The performance of the proposed scheme is demonstrated in dynamic simulation of an anthropomorphic compliant arm.

High-performance actuators are required for numerous novel applications such as human-robot assistive devices. The torque-to-weight ratio and energy efficiency of current actuation technology is often too low, which limits the performance of novel robots. Therefore, we developed a Series-Parallel Elastic Actuator (SPEA) which enables variable recruitment of parallel springs and variable load cancellation. Finding suitable intermittent mechanisms for the SPEA is however still challenging. This paper reports on the innovative design of an intermittent self-closing mechanism for a MACCEPA-based SPEA that can deliver bi-directional output torque and variable stiffness, while minimizing friction levels. Experiments on a one-layer intermittent self-closing mechanism are conducted to validate the working principle and the proposed model. A demonstrator of the MACCEPA-based SPEA with intermittent self-closing mechanism is presented and the experiments validate the modeled output torque and lowered motor torque for different stiffness settings.

In psychology the Rubber Hand Illusion (RHI) is an experiment where participants get the feeling that a fake hand is becoming their own. Recently, new testing methods using an action based paradigm have induced stronger RHI. However, these experiments are facing limitations because they are difficult to implement and lack of rigorous experimental conditions. This paper proposes a low-cost open source robotic hand which is easy to manufacture and removes these limitations. This device reproduces fingers movement of the participants in real time. A glove containing sensors is worn by the participant and records fingers flexion. Then a microcontroller drives hobby servo-motors on the robotic hand to reproduce the corresponding fingers position. A connection between the robotic device and a computer can be established, enabling the experimenters to tune precisely the desired parameters using Matlab. Since this is the first time a robotic hand is developed for the RHI, a validation study has been conducted. This study confirms previous results found in the literature. This study also illustrates the fact that the robotic hand can be used to conduct innovative experiments in the RHI field. Understanding such RHI is important because it can provide guidelines for prosthetic design.

Many robots capable of performing social behaviors have recently been developed for Human-Robot Interaction (HRI) studies. These social robots are applied in various domains such as education, entertainment, medicine, and collaboration. Besides the undisputed advantages, a major difficulty in HRI studies with social robots is that the robot platforms are typically expensive and/or not open-source. It burdens researchers to broaden experiments to a larger scale or apply study results in practice. This paper describes a method to modify My Keepon, a toy version of Keepon robot, to be a programmable platform for HRI studies, especially for robot-assisted therapies. With an Arduino microcontroller board and an open-source Microsoft Visual C# software, users are able to fully control the sounds and motions of My Keepon, and configure the robot to the needs of their research. Peripherals can be added for advanced studies (e.g., mouse, keyboard, buttons, PlayStation2 console, Emotiv neuroheadset, Kinect). Our psychological experiment results show that My Keepon modification is a useful and low-cost platform for several HRI studies.

Future robots will need to perform complex and versatile tasks comparable to those of humans. Due to the unavailability of suitable actuators, however, novel intelligent and agile robots are often restricted in their performances and development. The limited output torque range and low energy efficiency of current robotic actuators are the main bottlenecks. We have developed a SPEA with intermittent mechanism that addresses these problems. The SPEA is a novel compliant actuator concept that enables variable recruitment of parallel elastic elements and adaptive load cancellation. This paper describes how a SPEA lowers the motor torque and increases the energy efficiency. Experiments on the first proof of concept set-up endorse the practicability of the SPEA concept and the modeled trend of a lowered motor torque and increased energy efficiency. We expect that features of the biologically inspired SPEA with intermittent mechanism will prove exceedingly useful for robotics applications in the future.

In this paper, we describe the first results of using the robot Probo as a facilitator in Social Story Intervention for children with autism spectrum disorders (ASD). Four preschoolers diagnosed with ASD participated in this research. For each of them, a specific social skill deficit was identified, like sharing toys, saying Thank you, saying Hello, and an individualized Social Story was developed. The stories were told by both the therapist and the robot in different intervention phases. Afterwards an experimental task was created where the child needed to exercise the ability targeted by the story. The results of this study showed that the participant needed a decreased level of prompt to perform the targeted behavior, when the story was told by the robot compared to the intervention with the human storyteller. Therefore, this preliminary study created great expectancies about the potential of Robot Assisted Therapy as an added value for ASD interventions.

The work presents the standing stabilization of a compliant humanoid robot against external force disturbances and variations of the terrain inclination. The novel contribution is the proposed control scheme which consists of three strategies named compliance control in the transversal plane, body attitude control, and potential energy control, all combined with the intrinsic passive compliance in the robot. The physical compliant elements of the robot are exploited to react at the first instance of the impact while the active compliance control is applied to further absorb the impact and dissipate the elastic energy stored in springs preventing the high rate of spring recoil. The body attitude controller meanwhile regulates the spin angular momentum to provide more agile reactions by changing body inclination. The potential energy control module constrains the robot center of mass (COM) in a virtual slope to convert the excessive kinetic energy into potential energy to prevent falling. Experiments were carried out with the proposed balance stabilization control demonstrating superior balance performance. The compliant humanoid was capable of recovering from external force disturbances and moderate or even abrupt variations of the terrain inclination. Experimental data such as the impulse forces, real COM, center of pressure (COP) and the spring elastic energy are presented and analyzed.

Most of today's robots have rigid structures and actuators requiring complex software control algorithms and sophisticated sensor systems in order to behave in a compliant and safe way adapted to contact with unknown environments and humans. By studying and constructing variable impedance actuators and their control, we contribute to the development of actuation units which can match the intrinsic safety, motion performance and energy efficiency of biological systems and in particular the human. As such, this may lead to a new generation of robots that can co-exist and co-operate with people and get closer to the human manipulation and locomotion performance than is possible with current robots.

This paper discusses two ways to estimate the interaction force at the end-effector of a robot. The first approach that is presented combines filtered dynamic equations with a recursive least squares estimation algorithm to provide a smoothened force signal, which is useful in the (common) case of noisy torque measurements. The second approach, which uses a generalized momentum based disturbance observer, is mainly discussed to compare it to the first approach. Although very different in appearance, it is shown that a close connection exists between both approaches. Simulation results for both algorithms are shown, and experimental results derived from a sensorless admittance controller that was implemented using the algorithms are presented.

Most humanoid robots walk with bent knees, which particularly requires high motor torques at knees and gives an unnatural walking manner. It is therefore essential to design a control method that produces a motion which is more energy efficient and natural comparable to those performed by humans. In this paper, we address this issue by modeling the virtual spring-damper based on the cart-table model. This strategy utilizes the preview control, which generates the desired horizontal motion of the center of mass (COM), and the virtual spring-damper for generating the vertical COM motion. The theoretical feasibility of this hybrid strategy is demonstrated in Matlab simulation of a multi-body bipedal model. Knee joint patterns, ground reaction force (GRF) patterns, COM trajectories are presented. The successful walking gaits of the child humanoid "iCub" in the dynamic simulator validate the proposed scheme. The joint torques required by the proposed strategy are reduced, compared with the one required by the cart-table model.

This paper deals with a comparative study on using water and air as actuation means for the control of a fluidic muscle (designed for air) and assesses the performance, particularly from a dynamic and energetic point of view. A medium with higher bulk modulus such as oil/water is believed to increase pressure and force bandwidths and reduce sensitivity to load variations, as is the case with conventional hydraulic stiff actuation systems. However in this application the inherent flexibility of the muscle plays a major role. Water has been chosen because of its non-flammability, environmental friendliness and the low solubility of air in it. The operating pressure range of the pneumatic muscle is 0-6 bar (typical range of a pneumatic system) that is well below typical operating pressures of hydraulic systems (typically over 100 bar). At such low pressures the dynamic behaviour of water is less predictable because of the higher likelihood of entrapped air in the water which physically occurs when operating at low pressures. This can majorly affect water bulk modulus and hence its dynamic performance. Therefore, the behaviour of the system in this unconventional pressure range for a liquid must be more thoroughly investigated. Theoretical and experimental analyses on a dedicated test rig have been carried out to assess these assumptions.

This paper describes the design and development of a new actuator with adjustable stiffness (AwAS) which can be used in robots which are necessary to work close to or physically interact with humans, e.g. humanoids and exoskeletons. The actuator presented in this work can independently control equilibrium position and stiffness by two motors. The first motor controls the equilibrium position while the second motor regulates the compliance. The novelty of the proposed design with respect to the existing systems is on the principle used to regulate the compliance. This is done not through the tuning of the pretension of the elastic element as in the majority of existing system but by controlling the fixation of the elastic elements (springs) using a linear drive. An important consequence of this approach is that the displacement needed to change the stiffness is perpendicular to the forces generated by the springs, thus this helps to minimize the energy/power required to change the stiffness. This permits the use of a small motor for the stiffness adjustment resulting in a lighter setup. Experimental results are presented to show the ability of AwAS to control position and regulate the stiffness independently.

This paper presents the development of a new compact soft actuation unit intended to be used in multi degree of freedom and small scale robotic systems such as the child humanoid robot “iCub” [1]. Compared to the other existing series elastic linear or rotary implementations the proposed design shows high integration density and wider passive deflection. The miniaturization of the newly developed high performance unit was achieved with a use of a new rotary spring module based on a novel arrangement of linear springs.

The MACCEPA (Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator) is an electric actuator of which the compliance and equilibrium position are fully independently controllable and both are set by a dedicated servomotor. In this paper an improvement of the actuator is proposed where the torque-angle curve and consequently the stiffness-angle curve can be modified by choosing an appropriate shape of a profile disk, which replaces the lever arm of the former design. The actuator has a large joint angle, torque and stiffness range and these properties can be made beneficial for safe human robot interaction and the construction of energy efficient walking, hopping and running robots. The ability to store and release energy is shown by simulations on a 1DOF hopping robot. Its hopping height is much higher compared to a configuration in which the same motor is used in a traditional stiff setup. The stiffness of the actuator has a stiffening characteristic so the leg stiffness resembles more a linear stiffness as found in humans.

The ¿iCub¿ is a robotic platform that was developed within the RobotCub European project to provide the cognition research community with an open ¿child-like¿ humanoid platform for understanding and development of cognitive systems. In this paper we present the mechanical realization of the new lower body developed for the ¿iCub¿ child humanoid robot in order to keep up with the latest technology and solve mechatronic problems found in the previous version. The new lower body assembly demonstrates significant improvements over the old prototype including higher modularity, full joint state sensing and improved range of motion and torque capabilities. In particular the new leg and waist mechanisms to match the size and physical abilities of a 3¿ year old human child are introduced.

This study proposes a complete solution to make the humanoid robot HRP-2 dynamically step over large obstacles. As compared with previous results using quasistatic stability, where the robot crosses over a 15-cm obstacle in 40 s, our solution allows HRP-2 to step over the same obstacle in 4 s. This approach allows the robot to clear obstacles as high as 21% of the robot's leg length (15 cm) while walking. Simulations show the possibility to step over an obstacle that is 35% of the length (25 cm) with a margin of 3 cm.

Research in robotic gait rehabilitation still faces many challenges regarding ankle assistance, body weight support and human-robot interaction. This paper reports on the development, focusing on these challenges, of a gait rehabilitation exoskeleton powered by pleated pneumatic artificial muscles. The first prototype is intended as a platform for the evaluation of design and control concepts. The mechanical design procedure is explained with the emphasis on optimization. A proxy-based sliding mode control approach is proposed and evaluated by means of simulation. Simulation results indicate good tracking performance and safe system behavior, encouraging experimental validation on the prototype.

Kikuuwe and Fujimoto have introduced proxy-based sliding mode control. It combines responsive and accurate tracking during normal operation with smooth, slow recovery from large position errors that can sometimes occur after abnormal events. The method can be seen as an extension to both conventional PID control and sliding mode control. In this paper, proxy-based sliding mode control is used to control a 2-DOF planar manipulator actuated by pleated pneumatic artificial muscles (PPAMs). The principal advantage of this control method is increased safety for people interacting with the manipulator. Two different forms of proxy-based sliding mode control were implemented on the system, and their performance was experimentally evaluated. Both forms performed very well with respect to safety. Good tracking was also obtained, especially with the second form.

This video demonstrates our current investigation in developing autonomous behaviors for humanoid robots. Our main goal is to develop functionalities as much generic as possible in order to realize useful behaviors. More particularly this video demonstrates our current status on extending a popular zero momentum problem (ZMP) preview control based pattern generator, and building some links between walking with vision.

In this paper a novel rotational actuator with adaptable compliance is presented. First the importance of adaptable compliance for bipedal walking is explained, and then a number of comparable designs are given with their possible drawbacks. The MACCEPA concept and design is described in detail. The formula to calculate the generated torque is derived. It is shown, depending on the design parameters, that the torque is a quasi linear function with respect to the angle between equilibrium position and actual position. Also the change of the pre-tension has a quasi linear effect on the torque. Another advantage is that the actuator can be built with standard components, e.g. electrical servo motors. Experiments show the independent control of equilibrium position and compliance. Finally, the concept of controlled passive walking is explained, which is a combination of the control strategies of active and passive walking robots. Controlled passive walking requires actuators with adaptable compliance, preferably where the control of equilibrium position and compliance are independent

In the biped Lucy pleated pneumatic artificial muscles are used instead of electrical motors to power the joints, because in an antagonistic set-up both the torque and the compliance are controllable. The muscles have also a high power to weight ratio and they can reduce impact effects. Interesting characteristics that can be exploited for legged robots. In this paper a control strategy is discussed where a torque control unit tracks a predefined trajectory and a compliance controller is used to reduce control efforts and energy consumption by fitting the compliance of the actuator to the natural compliance of the desired trajectory. The first part of this paper focusses on the torque control unit for the biped. The proposed control architecture consists of the joint trajectory generator and the joint trajectory tracking controller. The trajectory generator calculates trajectories represented by polynomials based on objective locomotion parameters, which are average forward speed, step length, step height and intermediate foot lift. The joint trajectory tracking controller is divided in three parts: a computed torque module, a delta-p unit and a bang-bang pressure controller. Results of the incorporation of this control architecture in the real biped Lucy are given. Several essential graphs showing tracking performance and pressure regulation are given and the effectiveness of the control algorithm is discussed. A second part of the paper focusses on the compliance controller which is experimentally tested on a one DOF pendulum. A mathematical formulation to exploit the natural dynamics with respect to different walking patterns for this purpose is explained. The experimental results show the effectiveness and importance of the adaptation strategy

This paper reports on the control structure of the pneumatic biped Lucy. The robot is actuated with pleated pneumatic artificial muscles, which have interesting characteristics that can be exploited for legged machines. They have a high power to weight ratio, an adaptable compliance and they can reduce impact effects. The discussion of the control architecture focusses on the joint trajectory generator and the tracking controller which is divided in four parts: a computed torque module, an inverse delta-p unit, a local PI controller and a bang-bang pressure controller. The control design is divided into single support and double support where specifically the computed torque differs for these two phases. A full hybrid dynamic simulation model is used to evaluate the control architecture of the biped. This simulator combines the dynamical behaviour of the robot with the thermodynamical effects that take place in the muscle-valves system. The observed hardware limitations of the real robot and expected model errors are taken into account in order to give a realistic qualitative evaluation of the control performance and to test the robustness. Finally the first results of the incorporation of this control architecture in the real biped Lucy are given.